In-Jae Kim

Photoluminescence study on the effects of the surface of CdTe by surface passivation

The etching effects on the CdTe surface treated by the different chemical etchants, such as 2% Br-methanol (BM) and 2% Br-20% latic acid in ethylene glycol (BLE) solutions are studied by both photoluminescence (PL) and atomic force microscopy. After etching, the dielectric materials ZnS and CdZnTe are used for the passivation of the CdTe surface. The PL studies of the CdTe surfaces passivated by the dielectrics are carried out, and the results are correlated with the value of the lifetime of the CdTe. The results show that the etching of CdTe surface by BLE solution yields the better surface condition for CdTe. The surface trap states of CdTe are reduced by the CdZnTe and ZnS passivant which results in the increase in the surface lifetime of CdTe.

Study on the subband structure of HgCdTe surface by electron tunneling spectroscopy

In order to investigate the surface states of electron which can tunnel through the sufficiently thin insulator, the electron tunneling spectroscopy is used to measure the tunneling current in function of the bias voltage, and directly to get the subbands of accumulation layer. The tunneling current through ZnS barrier in the Hg1-xCdxTe-ZnS-In junction structure is measured by various applied bias at 77 K and 4.2 K. From the measurement at 77 K, the subband energy levels in the electron accumulation layer at the surface of n-type Hg1-xCdxTe are found to be located at -59 meV for the ground state and -13 meV for the first excited state relative to the Fermi level of Hg1-xCdxTe. At low temperature when the applied bias is larger than the difference between the work function of In and the electron affinity of ZnS, a negative differential resistance is measured. On the calculation using transfer matrix method it is understood that this negative conductance is attributed to Fowler-Nordheim tunneling which is caused by the variation of ZnS barrier according to the various applied bias.